Stem Cells Specialize Better in Polymer Gel

 May 30, 2012 By Dale McGeehon   A polymer gel created by researchers at the University of Michigan’s College of Engineering provides a culture to develop human stem cells that is free from biological contaminants unlike commonly used cultures that often contain animal cells and proteins.   About five years ago, scientists discovered that human specialized cells could be reprogrammed to behave like a more primitive stem cell that could, in turn, develop into any type of specialized cells that a patient may need, such as those for organs, nerves, skin, and bone. But before those stem cells could be used to make repairs in the body, they had to be grown in a culture with a gel that was expensive and whose contents varied.   “You don’t really know what’s in there,” says Joerg Lahann, an associate professor of chemical engineering and biomedical engineering, in a press release from the university. For example, human stem cells could be grown over mouse cells and therefore produce some mouse proteins that could prompt a human patient’s immune system to attack them.   So Lahann and his colleagues solved that problem by designing a polymer gel, controlling its ingredients and how they combine. “It’s basically the ease of a plastic dish,” he says. “There is no biological contamination that could potentially influence your human stem cells.”   Lahann and his colleagues had shown that the surfaces could grow embryonic stem cells. He took the next step by collaborating with Paul Krebsbach, a professor of biological and materials sciences in the university’s School of Dentistry, to show that the polymer gel also could grow induced stem cells, which are more medically promising, keeping them in their potential state. The team turned the embryonic stem cells into fat, cartilage, and bone cells.   Next, they tested to see whether these cells could help repair the body. They placed human bone cells into five-millimeter holes in the skulls of mice. After eight weeks, the mice that had received the bone cells had 4.2 times as much new bone and early formations of marrow cavities. The mice’s immune system did not attack the human bone cells that grew in the holes.   “The concept is not specific to bone,” says Krebsback. “If we truly develop ways to grow these cells without mouse or animal products, eventually other scientists around the world could generate their tissue of interest.”   In its next phase of research, Lahann’s team wants to use their polymer gel to grow stem cells and specialized cells in different physical shapes, such as a bone-like structure or a nerve-like microfiber. A paper explaining this research, titled “Derivation of Mesenchymal Stem Cells from Human Induced Pluripotent Stem Cells Cultured on Synthetic Substrates,” appears in Stem Cells.